Snake hook in sculpt mode is creating glitch like shapes instead of smoth tentacles
You need to enable Dyntopo in the left panel, otherwise the tool will only displace geometry, until it gets horribly mangled and creates artifacts.
Dyntopo will generate new geometry on the fly, provided you don't move your mouse too fast it should create a smooth hook.
Don't forget to tweak the detail size if you think the generated geometry doesn't fit.

Also consider using the latest version if you can, there has been gigantic improvements since 2.79 in the sculpting area.
Link to the official download page